/**
 * Copyright (c) 2005-2012 springside.org.cn
 */
package com.gitee.fdc.kits;

import java.io.StringReader;
import java.io.StringWriter;
import java.util.Collection;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.bind.annotation.XmlAnyElement;
import javax.xml.namespace.QName;

import org.springframework.http.converter.HttpMessageConversionException;
import org.springframework.util.Assert;

import org.apache.commons.lang3.StringUtils;

/**
 * 使用Jaxb2.0实现XML<->Java Object的Mapper.
 * 
 * 在创建时需要设定所有需要序列化的Root对象的Class. 特别支持Root对象是Collection的情形.
 * 
 * @author calvin
 * @version 2013-01-15
 */
@SuppressWarnings("rawtypes")
public class JaxbMapper {

    private static ConcurrentMap<Class, JAXBContext> jaxbContexts = new ConcurrentHashMap<Class, JAXBContext>();

    /**
     * Java Object->Xml without encoding.
     */
    public static String toXml(Object root) {
	Class clazz = Reflections.getUserClass(root);
	return toXml(root, clazz, null);
    }

    /**
     * Java Object->Xml with encoding.
     */
    public static String toXml(Object root, String encoding) {
	Class clazz = Reflections.getUserClass(root);
	return toXml(root, clazz, encoding);
    }

    /**
     * Java Object->Xml with encoding.
     */
    public static String toXml(Object root, Class clazz, String encoding) {
	try {
	    StringWriter writer = new StringWriter();
	    createMarshaller(clazz, encoding).marshal(root, writer);
	    return writer.toString();
	} catch (JAXBException e) {
	    throw Exceptions.unchecked(e);
	}
    }

    /**
     * Java Collection->Xml without encoding, 特别支持Root Element是Collection的情形.
     */
    public static String toXml(Collection<?> root, String rootName, Class clazz) {
	return toXml(root, rootName, clazz, null);
    }

    /**
     * Java Collection->Xml with encoding, 特别支持Root Element是Collection的情形.
     */
    public static String toXml(Collection<?> root, String rootName, Class clazz, String encoding) {
	try {
	    CollectionWrapper wrapper = new CollectionWrapper();
	    wrapper.collection = root;

	    JAXBElement<CollectionWrapper> wrapperElement = new JAXBElement<CollectionWrapper>(new QName(rootName),
		    CollectionWrapper.class, wrapper);

	    StringWriter writer = new StringWriter();
	    createMarshaller(clazz, encoding).marshal(wrapperElement, writer);

	    return writer.toString();
	} catch (JAXBException e) {
	    throw Exceptions.unchecked(e);
	}
    }

    /**
     * Xml->Java Object.
     */
    @SuppressWarnings("unchecked")
    public static <T> T fromXml(String xml, Class<T> clazz) {
	try {
	    StringReader reader = new StringReader(xml);
	    return (T) createUnmarshaller(clazz).unmarshal(reader);
	} catch (JAXBException e) {
	    throw Exceptions.unchecked(e);
	}
    }

    /**
     * 创建Marshaller并设定encoding(可为null). 线程不安全，需要每次创建或pooling。
     */
    public static Marshaller createMarshaller(Class clazz, String encoding) {
	try {
	    JAXBContext jaxbContext = getJaxbContext(clazz);

	    Marshaller marshaller = jaxbContext.createMarshaller();

	    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);

	    if (StringUtils.isNotBlank(encoding)) {
		marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
	    }

	    return marshaller;
	} catch (JAXBException e) {
	    throw Exceptions.unchecked(e);
	}
    }

    /**
     * 创建UnMarshaller. 线程不安全，需要每次创建或pooling。
     */
    public static Unmarshaller createUnmarshaller(Class clazz) {
	try {
	    JAXBContext jaxbContext = getJaxbContext(clazz);
	    return jaxbContext.createUnmarshaller();
	} catch (JAXBException e) {
	    throw Exceptions.unchecked(e);
	}
    }

    protected static JAXBContext getJaxbContext(Class clazz) {
	Assert.notNull(clazz, "'clazz' must not be null");
	JAXBContext jaxbContext = jaxbContexts.get(clazz);
	if (jaxbContext == null) {
	    try {
		jaxbContext = JAXBContext.newInstance(clazz, CollectionWrapper.class);
		jaxbContexts.putIfAbsent(clazz, jaxbContext);
	    } catch (JAXBException ex) {
		throw new HttpMessageConversionException("Could not instantiate JAXBContext for class [" + clazz
			+ "]: " + ex.getMessage(), ex);
	    }
	}
	return jaxbContext;
    }

    /**
     * 封装Root Element 是 Collection的情况.
     */
    public static class CollectionWrapper {

	@XmlAnyElement
	protected Collection<?> collection;
    }

}
